html {
  font-size: 12px;
  --container-width: 600px;
}

body {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: start;
  justify-content: flex-start;
}

* {
  box-sizing: border-box;
}

body > header,
body > footer,
body > .main__content {
  width: 100%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 1rem;
}

body > .main__content{
    flex: 1;
}